Note on
Taxonomy - Plant taxonomy is the art and
science of classifying plants into groupings in order to help people
make sense of the huge diversity found in the world. The people who
do this for a living are called taxonomists. They are continually
evaluating and re-evaluating how plants are classified. For example,
with the recent emergence of DNA analysis, many plants have been
changing classification.

Also, there is no
one, single universal classification system for plants. Rather,
there is a lot of debate among taxonomists which may lead to
confusion for the average gardener. That is why, in these family
listings, you often see the words "about" or "around" when counting
the number of genera or species to include. It is also why new
families are created and some of the old ones suddenly fade away.
So, don't be surprised if you find slightly different information at
other sites or sources. Oh, well.